This project develops new labeling techniques, generally applicable to the positron emitting radionuclides, oxygen-15, carbon-11 and fluorine- 18 as well as developing new syntheses for compounds that will be used in the other research projects. In the current proposal several areas are emphasized. These are: 1. The synthesis of O-15 labeled DOPA. 2. New approaches of omega-labeling of compounds, particularly palmitic acid. 3. Approaches to synthesizing an improved marker of hypoxic tissue. 4. New approaches to synthesis of proteins with carbon-11 and fluorine- 18. 5. Continued work on the fluorine-18-labeling of receptor ligands. 6. In vitro and in vivo evaluation of compounds developed in subsections 1 through 5.